Insight into the Effect of Counterions on the Chromatic Properties of Cr-Doped Rutile TiO2-Based Pigments

Abstract

Rutile TiO2 pigments codoped with chromophore ion Cr3+ and various charge-balancing ions (i.e., counterions species of Sb, Nb, W and Mo) were prepared by a solid-phase reaction method. The effects of the counterions and calcination temperatures on the phase structure, color-rendering and spectroscopic properties, microstructure, and stability of the synthesized pigments were investigated in detail. The results showed that the introduction of 5–10% counterions improved the solubility of Cr3+ in the TiO2 lattice to form the single-phase rutile pigments calcined at 1100 °C for 2 h. The 10% Cr-doped pigment showed a dark brown color. Depending on the content and type of counterions, the color of the codoped pigments was tailored from yellow to reddish or yellowish-orange to black with different brightness and hue. The influence mechanism of counterions was ascribed to the lattice distortion and variation in the charge balance condition. It was found that the addition of Sb, Nb, or Mo resulted in a remarkable improvement in the NIR reflectance of pigments. The grain growth was inhibited with the codoping of Cr/Sb and Cr/Nb to achieve the nano-sized pigments. In addition, the prepared pigments exhibited good acid and alkali corrosion resistance as well as excellent stability and coloring performance in transparent ceramic glazes.

Preparation of Environmentally Friendly BiVO4@SiO2 Encapsulated Yellow Pigment with Remarkable Thermal and Chemical Stability

“…Inorganic pigments have been applied in various products such as ceramics, enamels, paints/coatings, plastics, and glasses due to their high hiding power, weather resistance, UV stability, and thermal stability [1][2][3][4][5][6][7]. Among them, yellow pigments are particularly interesting because of their great applicability in many industries, such as the building, automotive, decorative paints, and plastics industries [7][8][9][10]. In particular, inorganic yellow pigments, with their striking color, are in great demand due to their usefulness in many applications.…”

“…Bismuth vanadate (BiVO 4 ), an eco-friendly type of yellow pigment, has attracted much attention due to its bright color, nontoxicity, and high hiding power [10][11][12][13][14]. This environmentally friendly inorganic yellow pigment has the potential to replace iron yellow, chrome yellow, cadmium yellow, nickel titanium yellow, and chromium titanium yellow pigments [7,15]. Simultaneously, because green or yellow is an eye-catching color, greenish-yellow BiVO 4 pigments can be used as traffic marks and building coatings, indicating that greenishyellow BiVO 4 pigments seem to be promising candidates in terms of pigment safety and environmental friendliness [10,14,16].…”